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Title: Multiservice ethernet digital distributed antenna systems
Author: Bai, Lu
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2019
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Over 90% of wireless communications traffic occurs indoors and in-building wireless coverage is still one of the biggest obstacles for wireless users. As the growing demands on wireless capacity, coverage and connectivity have led to 4G and 5G standards, it has also become increasingly important to design and implement future-proof indoor wireless services in a cost effective manner. This thesis introduces a novel multi-service digital distributed antenna systems (DDAS) for indoor wireless coverage, which not only is able to transport multiple wireless carriers from different vendors and mobile operators, but also allows a converged architecture to integrate indoor wireless system with existing Ethernet infrastructures. The Cloud Radio Access Networks (C-RAN) has been suggested by major telecom vendors as the main architecture for last-mile coverage in 5G. However, the digital fronthaul interface defined in common public radio interface (CPRI), which is most widely adopted standard for C-RAN, requires very expensive infrastructures to be built due to the high data rate generated after digitisation. A solution has been introduced at the University of Cambridge previously to remove the digital redundancy by using a data compression technique which has shown 3-times higher transmission efficiency than CPRI. This thesis extends the concept to a more robust architecture allowing multiple wireless services to be transmitted simultaneously as well as being carried over standard Ethernet without losing the Quality of End-user Experience (QoE) and the Quality of Service (QoS) of in-building mobile network. A two-channel DDAS system with data compression algorithm is experimentally demonstrated, showing wide RF dynamic range for both 4G LTE service and 3G WCDMA service simultaneously carried over a single fibre-based infrastructure. The system leads to the design and implementation of full-service DDAS system allowing 14 channels (all 2/3/4G service from three major mobile operators) to be carried over single 10Gbps network. Typically, the system using CPRI will need over 30Gbps network to be installed for wireless coverage. Another key aspect covered in this thesis is the design and implementation of the multi-service DDAS over Ethernet (Eth-DDAS). Due to the stringent latency requirement in wireless services, mitigation of delays and errors in frame ordering has become a key challenge for putting DDAS over Ethernet. To overcome these problems, a special Eth-DDAS frame structure is proposed in this thesis. After digitisation, digital signal bearing RF information is packetised onto Ethernet-compatible frames with additional timestamps and sequence numbers before transported via fibre to the receiver. Three latency scenarios are tested with different payload sizes of the proposed frame structure and real-time RF performance is measured to prove the capability of implementation of such system in real-life using commercial off-the-shelf (COTS) ADC/DAC and FPGAs.
Supervisor: White, Ian Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Digital Distributed Antenna Systems ; wireless system ; RF over Ethernet